Pandas read_csv() - ValueError: cannot set a row with mismatched columns

Question

Here's is my Python code:

import pandas as pd
data = [{'Countries':[],2016:[],2017:[],2018:[],2019:[]}]
df = pd.DataFrame(data)

opt='y'
while(opt=='y'):
    print("1. Add a new record to the end of the file")
    print("2. Display the selected records")
    print("3. Delete a Student record")
    print("4. Update a Student record")
    print("5. Reports of Students")
    ch=int(input("Enter your choice"))
    if ch==1:
        df=pd.read_csv("info.csv")
        i=len(df)
        cntry=input("Enter country name")
        i=int(input("Enter international tourism arrival rate in 2016"))
        ii=int(input("Enter international tourism arrival rate in 2017"))
        iii=int(input("Enter international tourism arrival rate in 2018"))
        iv=int(input("Enter international tourism arrival rate in 2019"))
        df.loc[cntry]=[i,ii,iii,iv]
        df.to_csv("info.csv")
        print("A new record is successfully inserted\n\n")
    elif ch==2:
      df=pd.read_csv("info.csv")
      print(df)
    opt=input("want to continue")

My CSV file:

Country,2016,2017,2018,2019
France,82.5,86.4,87.1,89.4
US,80.3,81.9,82.2,82.8
China,74.2,76.9,77.6,79.6
Italy,59.5,60.7,61.5,62.9
Turkey,55.6,58.3,60.1,62.1
Germany ,35.3,37.6,40.5,45.8
Thailand,37.5,37.5,38.2,38.9
UK,34.2,35.6,36.4,38.2
Japan,36.7,37.7,35.4,36.3
Greece,25.6,28.7,30.5,31.2
Malaysia,26.3,27.2,29.6,30.1
Russia Fed,25.6,27.9,30.3,29.3
Canada,24.8,25.9,26.7,25.8
Poland,23.4,24.4,25.2,24.6
India,20.1,21.2,22.3,22.6

I was trying to add more entries to the file, it took in all the data required but it showed this error:

    Traceback (most recent call last):

  File "C:\Users\Dell\OneDrive\Desktop\agj.py", line 22, in <module>
    df.loc[cntry]=[i,ii,iii,iv]

  File "C:\Users\Dell\anaconda3\lib\site-packages\pandas\core\indexing.py", line 670, in __setitem__
    self._setitem_with_indexer(indexer, value)

  File "C:\Users\Dell\anaconda3\lib\site-packages\pandas\core\indexing.py", line 874, in _setitem_with_indexer
    return self._setitem_with_indexer_missing(indexer, value)

  File "C:\Users\Dell\anaconda3\lib\site-packages\pandas\core\indexing.py", line 1118, in _setitem_with_indexer_missing
    raise ValueError("cannot set a row with mismatched columns")

ValueError: cannot set a row with mismatched columns

Does this answer your question? [Getting error when adding a new row to my existing dataframe in pandas](https://stackoverflow.com/questions/45104991/getting-error-when-adding-a-new-row-to-my-existing-dataframe-in-pandas) — Pouya Esmaeili, Nov 28 '20 at 18:18

score 2 · Accepted Answer · answered Nov 28 '20 at 21:04

The problem is that you have not set 'Country' as the index, it is treated as just the first column of the dataframe.

therefore,

df.loc[cntry]=[i,ii,iii,iv]

should have 5 elements in the array. also this doesn't make sense because cntry has not been set to index yet.

The way to fix this is to set country to be the index of the dataframe, like so

df.set_index('Country', inplace=True)

Pandas read_csv() - ValueError: cannot set a row with mismatched columns

1 Answers1